Did the climate of political rhetoric help lead to the assassination attempt on Arizona Representative Gabby Giffords and the deaths of six others? Was it the act of a single mentally unstable person? Could it be both?

Many people weighed in during that conversation, and many other continue to weigh in as well. Of course, unless the shooter tells us exactly why we will never know for certain, but the answer is important. Thanks to a recent post by Nate Silver called A Bayesian Take on Julian Assange, I think we can actually place a likelihood on our answer using Bayesian statistics.

It is worth reading Nate Silver’s entire post, but the take home point is that if you don’t take the larger context into account, you will form a bad estimate of the likelihood. In this case of the Arizona shooting, I think think it’s fair to say that there is an “upsurge in political hatred”, as Paul Krugman put it when he compared it to the time leading up to the Oklahoma City bombing. Given this larger context, we must conclude that the heated and threatening political rhetoric coming from conservatives likely contribute to actions of the shooter.

This is a nice little summary from Streetsblog debunking the idea that roads pay for themselves. Note that the original report referenced in that link considers only highways, meaning that the street network making up cities, suburbs and rural routes isn’t being considered.